1. Field of the Invention
The present invention relates to a plastic lens and a copolycarbonate resin to be used therefor. More specifically, it relates to a plastic lens and a copolycarbonate resin having transparency, heat resistance and impact resistance at high levels, having a well balance between a refractive index and an Abbe""s number and having a low birefringence. The copolycarbonate resin of the present invention is excellent in the above optical properties and physical properties, so that it can be applied not only to various plastic lenses but also other optical molded articles, and since it is also excellent in flowability, it is suitable for easily molding and processing these molded articles.
2. Prior Art
A polycarbonate resin (to be sometimes referred to as xe2x80x9cPCxe2x80x9d hereinafter) is a polymer formed by bonding bisphenols with carbonate ester, and above all, a polycarbonate resin obtained from 2,2-bis(4-hydroxyphenyl)propane (so-called bisphenol A) is excellent in transparency and heat resistance and has properties excellent in mechanical properties such as impact resistance, so that it is used in many fields. In the optical fields of various lenses and optical disks, it attracts attention to its properties such as impact resistance, transparency and low water absorption, and it holds an important position as a material for optical use.
In the field of lenses in particular, PC that is a thermoplastic resin is of great interest thanks to excellent productivity and processibility, and demands thereof are increasing as a substitute for thermosetting resins typified by CR-39 (diethylene glycol bisallyl carbonate) that has been a mainstream material for plastic lenses.
However, a polycarbonate resin obtained by reacting bisphenol A with phosgene or a carbonate precursor substance such as diphenyl carbonate has a high refractive index of 1.585 but has a low Abbe""s number of 30, so that it is liable to suffer a chromatic aberration problem and has a defect that it has a poor balance between the refractive index and the Abbe""s number. Further, it has a defect that it has a large photoelasticity constant whereby molded article therefrom comes to have a large birefringence.
For overcoming the above defects of the polycarbonate resin, there have been proposed some copolycarbonate resins formed from bisphenols and aliphatic diols (JP-A-1-66234, JP-A-10-120777, JP-A-11-228683, JP-A-11-349676 and JP-A-2000-63506). These techniques involve problems that polycarbonate resins have a low refractive index and a low Abbe""s number, that polycarbonate resins have a large photoelasticity constant and therefore come to have a large birefringence, that the moldability, heat resistance, etc., thereof are insufficient for obtaining satisfactory molded articles and that polycarbonate resins are colored.
It is a first object of the present invention to provide a plastic lens, particularly, a spectacle lens, which is excellent in transparency, heat resistance and impact resistance.
It is a second object of the present invention to provide a plastic lens, particularly, a spectacle lens, which has a good balance between refractive index and an Abbe""s number and has a refractive index and an Abbe""s number at good levels, and which has a low photoelasticity constant.
It is a third object of the present invention to provide an optical molded article having the above physical properties and optical properties.
It is another object of the present invention to provide a copolycarbonate resin that is suitable for producing the above plastic lens and the above optical molded article and has excellent flowability.
It is still another object of the present invention to provide means that permits production of a copolycarbonate resin having the above various excellent properties at a relatively low cost by selecting industrially advantageous raw materials and polymerization method(s).
For overcoming the above problems, the present inventors have made studies in various ways and as a result have found that a lens formed of a copolycarbonate resin obtained from a dihydroxy compound component containing constant amounts of cyclohexanedimethanol and a specific bisphenol achieves the above objects of the present invention, and the present invention has been accordingly reached.
That is, according to the present invention, there is provided a plastic lens formed of a copolycarbonate resin comprising a structural unit (I) of the following general formula (I), 
and a structural unit (II) of the following formula (II), 
the structural unit (I) having a molar amount percentage of 15 to 85% on the basis of the total amount of the structural units (I) and (II).
In the above structural unit (II), each of R1 and R2 is independently a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a cycloalkyl group having 6 to 20 carbon atoms, a cycloalkoxy group having 6 to 20 carbon atoms, an aryl group having 6 to 10 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, an aryloxy group having 6 to 10 carbon atoms or an aralkyloxy group having 7 to 20 carbon atoms, each of q and r is independently an integer of 0 to 4, W is a group represented by 
wherein each of R3 and R4 are the same as, or different from, each other and each is a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms, each of R5 and R6 is independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, p is an integer of 4 to 7, and each of R7 and R8 is independently a hydrogen atom, a halogen atom or an alkyl group having 1 to 3 carbon atoms.
The plastic lens of the present invention is not only excellent in transparency, impact resistance and heat resistance but also has a good balance between a refractive index and an Abbe""s number, and it also has a low photoelasticity constant, so that it is particularly suitable as a spectacle lens. Moreover, it has high surface hardcoating properties and high impact resistance, so that there is provided a spectacle lens that has a small thickness but has high practical utility.
As far as the present inventors have searched for literatures, there are some literatures on copolycarbonate resins obtained by polymerizing cyclohexanedimethanol (CHDM) as a dihydroxy component together with bisphenol. Such literatures will be briefly described below.
(1) U.S. Pat. No. 4,501,875 (JP-A-59-74121)
This literature describes a copolycarbonate resin that is improved in processability by reacting dihdyric phenol and bishaloformate of aliphatic (or alicyclic) glycol with phosgene. Specifically, it is only described that a polycarbonate obtained by copolymerization of 4 mol % of bischloroformate of CHDM and bisphenol A is improved in flowability (melt flow) as compared with a polycarbonate obtained from bisphenol A alone, and that the thus-obtained polycarbonate shows a impact resistance value, a loaded flexure temperature and ductility nearly equivalent to those of the polycarbonate obtained from bisphenol A alone.
(2) JP-A-63-92642
This literature describes that a copolycarbonate obtained by ester exchange of bisphenol A and 2 to 4 mol %, based thereon, of CHDM with diphenyl carbonate is used as an optical disk substrate.
(3) JP-A-8-302005
This literature describes that a copolycarbonate is obtained by polymerization of bisphenol A and CHDM (4 mol %) with diphenyl carbonate according to an ester exchange reaction, that a large amount of the diphenyl carbonate is used in this case so that a polymer whose hydroxy terminal group content is extremely decreased can be obtained, and that the above polymer is improved in hydrolysis resistance.
(4) European Polymer Journal, Vol. 12, pp 279-282 (1976)
This literature describes that a copolycarbonate is obtained by uniform-solution polymerization of bisphenol A and CHDM with phosgene in a methylene chloride solvent in the presence of pyridine as an acid binder and that a copolycarbonate containing 1 to 50 mol % of CHDM is obtained in this case, and it also describes results of measurement of molecular weights by a GPC method and results of measurements of physical properties (tensile stress and breaking elongation). This literature describes nothing concerning the use of the obtained copolycarbonate and its optical use in particular.
(5) Polymer, 1983, Vol. 24, October pp. 1313-1316
This literature describes that a 50/50 (molar ratio) alternate copolycarbonate of bisphenol A and CHDM is obtained, and that the alternate copolycarbonate is obtained by uniform-solution polymerization of chloroformate of bisphenol A and CHDM in a methylene chloride solvent in the presence of pyridine as an acid binder, and it also describes results of measurement of physical properties (viscosity, glass transition point and aging characteristic) for comparing the above polycarbonate with a random copolycarbonate. This literature describes nothing concerning the use of the alternate copolycarbonate and its optical use in particular.
The plastic lens and the copolycarbonate resin provided by the present invention will be explained more in detail hereinafter.
The copolycarbonate resin of the present invention is formed of the following structural units (I) and (II) as already described, and the amount ratio of the structural unit (I) by molar percentage based on the total amount of the structural units (I) and (II) is 15 to 85%, preferably 20 to 80%. 
wherein R1, R2, W, q and r are as defined concerning the foregoing structural unit (II).
The above structural units (I) and (II) are units formed by using cyclohexanedimethanol of the following formula (I-R) and bisphenol of the following formula (II-R) as dihydroxy compound components in the production of the polycarbonate resin. 
In the formula (II-R), R1, R2, W, q and r are as defined concerning the foregoing structural unit (II).
With regard to the cyclohexanedimethanol (I-R) and the bisphenol (II-R) as dihydroxy compounds for use in the production of the copolycarbonate resin of the present invention, specific compounds thereof will be explained below.
The cyclohexanedimethanol of the above formula (I-R) may be a cis-isomeric compound or a trans-isomeric compound or a mixture of a cis-isomeric compound and a trans-isomeric compound, and it includes 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol and 1,4-cyclohexanedimethanol. Of these, 1,4-cyclohexanedimethanol is preferred. These compounds may be used alone or in combination of two or more.
Preferably, 1,4-cyclohexanedimethanol is used as a cyclohexanedimethanol, and it has a trans/cis ratio in the range of from 100/0 to 50/50. The trans/cis ratio is more preferably 100/0 to 60/40, still more preferably 100/0 to 70/30, most preferably 100/0 to 80/20. With an increase in the amount ratio of the trans-isomeric compound, the glass transition temperature (Tg) of the copolycarbonate resin obtained increases, so that the copolycarbonate resin is improved in heat resistance. That is, in case that the 1,4-cyclohexanedimethanol/bisphenol A molar ratio for copolycarbonate resins is 50/50, when the 1,4-cyclohexanedimethanol has a trans/cis ratio of 50/50, the resin has a glass transition temperature (Tg) of 89xc2x0 C., and when the 1,4-cyclohexanedimethanol has a tarns/cis ratio of 99/1, the resin has a glass transition temperature (Tg) of 96xc2x0 C. For obtaining 1,4-cyclohexanedimethanol having a highest tarns/cis ratio, there can be employed a method that is known per se. For example, 1,4-cyclohexanedimethanol having a high trans-isomeric compound content can be obtained by repeating recrystallization in an organic solvent.
The bisphenol of the above formula (II-R) is preferably a group of the formula (II-R) in which W is 
wherein R3, R4, R5, R6, R7, R8 and p are as defined concerning the foregoing structural unit (II). Specific examples of the bisphenol include 4,4xe2x80x2-dihydroxybiphenyl, bis(4-hydroxyphenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(3-methyl-4-hydroxyphenyl)propane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 2,2-bis(3-phenyl-4-hydroxyphenyl)propane, 2,2-bis(3-isopropyl-4-hydroxyphenyl)propane, 2,2-bis(3-t-butyl-4-hydroxyphenyl)propane, 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)octane, 2,2-bis(3-bromo-4-hydroxyphenyl)propane, 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane, 2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, 2,2-bis(3-cyclohexyl-4-hydroxyphenyl)propane, 1,1-bis(3-cyclohexyl-4-hydroxyphenyl)cyclohexane, bis(4-hydroxyphenyl)diphenylmethane, 9,9-bis(4-hydroxyphenyl)fluorene, 9,9-bis(4-hydroxy-3-methylphenyl)fluorene, 1,1-bis(4-hydroxyphenyl)cyclopentane, 4,4xe2x80x2-dihydroxydiphenyl ether, 4,4xe2x80x2-dihydroxy-3,3xe2x80x2-dimethyldiphenyl ether, 4,4xe2x80x2-dihydroxydiphenylsulfone, 4,4xe2x80x2-dihydroxydiphenylsulfoxide, 4,4xe2x80x2-dihydroxydiphenylsulfide, 3,3xe2x80x2-dimethyl-4,4xe2x80x2-dihydroxydiphenylsulfide, 3,3xe2x80x2-dimethyl-4,4xe2x80x2-dihydroxydiphenylsulfoxide, 3,3xe2x80x2-dimethyl-4,4xe2x80x2-dihydroxydiphenylsulfone, 4,4xe2x80x2-dihydroxy-3,3xe2x80x2-diphenylsulfide, 4,4xe2x80x2-dihydroxy-3,3xe2x80x2-diphenylsulfoxide, 4,4xe2x80x2-dihydroxy-3,3xe2x80x2-diphenylsulfone, 1,3-bis{2-(4-hydroxyphenyl)propyl}benzene and 1,4-bis{2-(4-hydroxyphenyl)propyl}benzene. Of these, preferred are 1,1-bis(4-hydroxyphenyl)-1-phenylethane, 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(3-methyl-4-hydroxyphenyl)propane, 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 4,4xe2x80x2-dihydroxydiphenylsulfone, 3,3xe2x80x2-dimethyl-4,4xe2x80x2-dihydroxydiphenylsulfone, 9,9-bis(4-hydroxy-3-methylphenyl)fluorene, 1,3-bis{2-(4-hydroxyphenyl)propyl}benzene and 1,4-bis{2-(4-hydroxyphenyl)propyl}benzene. More preferred are 2,2-bis(4-hydroxyphenyl)propane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 4,4xe2x80x2-dihydroxydiphenylsulfone and 9,9-bis(4-hydroxy-3-methylphenyl)fluorene. Particularly preferred is 2,2-bis(4-hydroxyphenyl)propane (so-called bisphenol A) or 1,1-bis(4-hydroxyphenyl)cyclohexane. These may be used alone or in combination of two or more.
When the total molar percentage of structural units of the copolycarbonate resin of the present invention is taken as 100%, the molar percentage of the structural unit of the general formula (I) is 15 to 85%, preferably 20 to 80%, more preferably 20 to 70%, still more preferably 30 to 70% most preferably 30 to 50%. When the molar percentage of the structural unit (I) exceeds 85%, the copolycarbonate resin is sometimes caused to suffer a decrease in heat resistance and a decrease in refractive index. When it is less than 15%, the copolycarbonate resin has a decreased Abbe""s number and has a poor balance between a refractive index and an Abbe""s number, so that the copolycarbonate resin is undesirable as a lens material.
The copolycarbonate resin to be used for the plastic lens of the present invention has a relatively low polymerization degree value in view of processability and optical properties. That is, the polymerization degree in terms of a specific viscosity is properly in the range of from 0.3 to 0.6, preferably in the range of from 0.3 to 0.56. The copolycarbonate resin having a specific viscosity in the above range has excellent flowability (Q value) as will be described later, and it is easily moldable by melt injection molding. Further, a lens obtained is almost free of an optical strain.
The copolycarbonate resin of the present invention has excellent flowability during melting and has a very high value of flowability (Q value) measured according to a measurement method to be described later. While a homopolycarbonate resin from bisphenol A has a flowability (Q value) of 4.2xc3x9710xe2x88x923 cm3/s, the flowability (Q value) of the copolycarbonate resin of the present invention is from 20xc3x9710xe2x88x923 to 200xc3x9710xe2x88x923 cm3/s, preferably 25xc3x9710xe2x88x923 to 200xc3x9710xe2x88x923 cm3/s, most preferably 35xc3x9710xe2x88x923 to 180xc3x9710xe2x88x923 cm3/s.
The plastic lens of the present invention has relatively high levels of a refractive index and an Abbe""s number since it is formed of the above copolycarbonate resin, and these values are well-balanced, so that the plastic lens of the present invention is suitable for a spectacle. That is, the refractive index of the plastic lens of the present invention is in the range of from 1.500 to 1.600, preferably from 1.530 to 1.590, most preferably from 1.540 to 1.580 and Abbe""s number of the plastic lens of the present invention is in the range of from 31 to 48, preferably from 32 to 45.
The copolycarbonate resin for forming the plastic lens of the present invention has preferred modes with regard to its terminal groups and a molecular weight distribution. The above copolycarbonate resin has a terminal group formed of a phenolic hydroxyl group (OH group) derived from the bisphenol used as a source monomer. Advantageously, the content of terminals formed of a phenolic hydroxyl group (OH group) each based on the total amount of terminal groups thereof is in the range of from 1 to 80 mol %, preferably in the range of from 2 to 70 mol %. The terminal groups of the copolycarbonate resin are substantially formed of phenolic hydroxyl terminal group and aryl or alkyl terminal groups (e.g., phenyl group, substituted phenyl group, methyl group or ethyl group) having no phenolic hydroxyl group. The xe2x80x9ctotal amount of terminal groupsxe2x80x9d therefore substantially means the total amount of the phenolic hydroxyl groups and the above aryl or alkyl terminal groups.
The present invention therefore uses a copolycarbonate resin having a phenolic hydroxyl terminal group of 1 to 80 mol % when the above total amount is taken as 100 mol %.
Meanwhile, the copolycarbonate resin of the present invention preferably has a constant range of a molecular weight distribution. The above molecular weight distribution in terms of a weight average molecular weight (Mw)/number average molecular weight (Mn) (Mw/Mn) is in the range of from 1.1 to 3, preferably in the range of from 1.3 to 2.8, and a copolycarbonate resin having a molecular weight distribution in such a range is advantageously used. The above weight average molecular weight (Mw) and number average molecular weight (Mn) are determined on the basis of measurement methods to be described later.
The copolycarbonate resin having the above terminal groups and the above molecular weight distribution can be obtained by controlling the amount ratio of a carbonate ester and reaction conditions in a method in which polymerization is carried out to produce the resin by ester exchange method using the carbonate ester (diphenyl carbonate in particular) as a carbonate precursor, as will be explained later.
The copolycarbonate resin having the above terminal groups and the above molecular weight distribution is excellent in processability of a lens, a lens obtained is excellent in heat resistance, impact resistance and hue, and the processability in processing a lens surface for forming a hard coating layer is made easy, which serves to form a uniformly and strongly bonding hard coating layer.
The polymerization method for producing the copolycarbonate resin of the present invention will be explained below.
The production of the copolycarbonate resin of the present invention uses cyclohexanedimethanol of the following formula (I-R) and bisphenol of the following formula (II-R) as main dihydroxy compounds. 
In the formula (II-R), R1, R2, W, q and r are as defined concerning the foregoing structural unit (II).
The polymerization method is preferably selected from a method (solution polymerization method) in which the above two dihydroxy compounds and phosgene are reacted in the presence of an acid binder or a method (ester exchange method) in which the above two dihydroxy compounds are ester-exchanged with a carbonate ester.
Of these, the ester-exchange method is advantageous. The ester-exchange method is not limited in polymerization mode and method. For example, both a melt polymerization method and a solid phase polymerization method may be employed, and the melt polymerization method is industrially desirable.
In the solution polymerization method, the acid binder includes aromatic tertinary amines such as pyridine, quinoline, isoquinoline and dimethylaniline, and pyridine is particularly preferably used. The reaction is carried out in the presence of the acid binder alone, or the acid binder dilated by an organic solvent in a solution. The above organic solvent is selected from hydrocarbons such as benzene, toluene and xylene or halogenated hydrocarbons such as methylene chloride, chloroform, dichloroethane, chlorobenzene and dichlorobenzene. Particularly, halogenated hydrocarbons such as methylene chloride, chloroform, dichloroethane, chlorobenzene and dichlorobenzene are preferred, and methylene chloride is the most preferred. The amount of the acid binder based on phosgene is generally 2 to 100 mole equivalent weights, preferably 2 to 50 mole equivalent weights. The reaction temperature is generally 0 to 100xc2x0 C., preferably 0 to 40xc2x0 C. The reaction time period is generally several minutes to several days, preferably 10 minutes to 5 hours. Further, a monofunctional phenol may be used as a terminal stopper. The monofunctional phenol is generally used as a terminal stopper for adjusting a molecular weight, and the thus-obtained copolycarbonate resin comes to have terminals that are blocked with groups based on the monofunctional phenol. Specific examples of the above monofunctional phenol include phenol, p-tert-butylphenol, p-cumylphenol and isooctylphenol. Further, as other monofunctional phenol, there may be used a phenol or benzoic acid chloride having a long-chain alkyl group or aliphatic polyester group as a substituent or a long-chain alkylcarboxylic acid chloride.
Desirably, the above terminal stopper is introduced into terminals such that the content thereof based on the amount of the total terminals of the polycarbonate resin obtained is at least 5 mol %, preferably at least 10 mol %. The above terminal stoppers may be used alone or in combination of two or more.
In the melt-polymerization method according to the ester-exchange method, the dihydroxy compounds and the carbonate ester are mixed under heat in the presence of an inert gas, and a formed alcohol or phenol is distilled off. While the reaction temperature differs depending upon the boiling point of the formed alcohol or phenol, it is generally in the range of from 120 to 350xc2x0 C. At a later stage of the reaction, the reaction system is pressure-reduced to approximately 1,330 to 13.3 Pa to easily distill off the formed alcohol or phenol. The reaction time period is generally approximately 1 to 10 hours.
The carbonate ester includes esters of an optionally substituted aryl group having 6 to 12 carbon atoms, an aralkyl group or an alkyl group having 1 to 4 carbon atoms. Specific examples thereof include diphenyl carbonate, bis(chlorophenyl)carbonate, dinaphthyl carbonate, bis(diphenyl)carbonate, dimethyl carbonate, diethyl carbonate and dibutyl carbonate, and of these, diphenyl carbonate is preferred.
The amount of the carbonate ester per mole of the dihydroxy compounds is preferably in the range of from 0.97 to 1.2 mol, particularly preferably in the range of from 1.0 to 1.1 mol.
In the ester-exchange method, a polymerization catalyst can be used for increasing the polymerization rate. The polymerization catalyst can be selected from catalysts that are generally used for esterification reactions and ester-exchange reactions. Examples of the polymerization catalyst include alkali metal compounds such as sodium hydroxide, potassium hydroxide and sodium salt or potassium salt of a dihydric phenol; alkaline earth metal compounds such as calcium hydroxide, barium hydroxide and magnesium hydroxide; nitrogen-containing basic compounds such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, timethylamine and triethylamine; alkoxides of alkali metals or alkaline earth metals; organic acid salts of alkali metals or alkaline earth metals; zinc compounds; boron compounds; aluminum compounds; silicon compounds; germanium compounds, organotin compounds; lead compounds; osmium compounds; antimony compounds; manganese compounds; titanium compounds; and zirconium compounds. The above catalysts may be used alone or in combination of two or more. The amount of the polymerization catalyst per mole of the dihydroxy compounds as raw materials is preferably in the range of from 1xc3x9710xe2x88x929 to 1xc3x9710xe2x88x922 equivalent weight, more preferably in the range of from 1xc3x9710xe2x88x928 to 5xc3x9710xe2x88x923 equivalent weight.
Further, a molecular weight adjusting agent, an antioxidant, etc., may be added as required.
A catalyst deactivator may be added to the obtained copolycarbonate. As a catalyst deactivator, known catalyst deactivators are effectively used. Of these, ammonium salts and phosphonium salts of sulfonic acids are preferred. Further preferred are the above salts of dodecylbenzenesulfonic acid such as tetrabutylphosphonium salt of dodecylbenzenesulfonic acid, and the above salts of p-toluenesulfonic acid such as tetrabutylammonium salt of p-toluenesulfonic acid. As an ester of sulfonic acid, there are preferably used methyl benzenesulfonate, ethyl benzenesulfonate, butyl benzenesulfonate, octyl benzenesulfonate, phenyl benzenesulfonate, methyl p-toluenesulfonate, ethyl p-toluenesulfonate, butyl p-toluenesulfonate, octyl p-toluenesulfonate and phenyl p-toluenesulfonate. Of these, tetrabutylphosphonium salt of dodecylbenzenesulfonic acid is the most preferred.
The amount of the above catalyst deactivator per mole of the above polymerization catalyst selected from the alkali metal compounds and/or the alkaline earth metal compounds is 0.5 to 50 mol, preferably 0.5 to 10 mol, more preferably 0.8 to 5 mol. The catalyst deactivator can be used in such an amount ratio.
According to studies made by the present inventors, the copolycarbonate resin of the present invention varies to some extent in physical properties, particularly, glass transition temperature and flowability (Q value) depending upon a polymerization method. It is assumed that the above variation is caused by a difference in amount ratio of the structural unit (I) and the structural unit (II) alternately arranged on a main polymer chain as described later.
That is, the copolycarbonate resin of the present invention is constituted of two carbonate bond types, one having a structure (i) in which a carbonate bond (xe2x80x94Oxe2x80x94COxe2x80x94Oxe2x80x94) forms a center, the structural unit (I) bonds to one side of the central carbonate bond and the structural unit (II) bonds to the other side (to be referred to as xe2x80x9chetero-carbonatexe2x80x9d hereinafter) and the other having a structure (ii) in which a carbonate bond (xe2x80x94Oxe2x80x94COxe2x80x94Oxe2x80x94) forms a center and the structural units (I) bond to both the sides or the structural units (II) bond to both the sides (to be referred to as xe2x80x9chomo-carbonatexe2x80x9d hereinafter).
A polycarbonate having a unit from 1,4-cyclohexanedimethanol as the structural unit (I) and a unit from bisphenol A as the structural unit (II) will be explained as an example. The hetero-carbonate (C-1) and the homo-carbonates (C-2 and C-3) are represented by the following chemical structural formulae. 
When 1,4-cyclohexanedimethanol and bisphenol A are used in an amount ratio of 50/50 (mol %) as dihydroxy compounds for the production of the copolycarbonate resin, and if it is assumed that the reaction proceeds on the basis of a probability theory, the ratio of the above hetero-carbonate (C-1): homo-carbonate (C-2): homo-carbonate (C-3) comes to be 50:25:25. That is, the hetero-carbonate (C-1): homo-carbonates (C-2+C-3) ratio is calculated to be 50:50.
However, the present inventors have conducted experiments and found that when 1,4-cyclohexanedimethanol and bisphenol A are used in an amount ratio of 50/50 (mol %) as dihydroxy compounds to produce a copolycarbonate resin, the thus-obtained resin does not necessarily have a hetero-carbonate (C-1):homo-carbonates (C-2+C-3) ratio of 50:50, and that the above ratio varies to some extent depending upon a polymerization method.
In a solution polymerization method using an aromatic tertiary amine such as pyridine as the above acid binder and phosgene as a carbonate precursor, there is obtained a copolycarbonate resin having a hetero-carbonate:homo-carbonates ratio, for example, of 44:56 in which the amount ratio of the hetero-carbonate is very close to a probability theory. In a melt polymerization method using carbonate ester (e.g., diphenyl carbonate) as a carbonate precursor, there is obtained a copolycarbonate resin having a hetero-carbonate:homo-carbonates ratio, for example, of 70:30 in which the amount ratio of the hetero-carbonate is considerably high over 50 mol %. The above examples of the solution polymerization method and the melt polymerization method show cases where 1,4-cyclohexanedimethanol and bisphenol A were used in an amount ratio of 50/50 (mol %) as dihydroxy compounds. As will be clear from Examples to be described later, the amount ratio of the hetero-carbonate and the homo-carbonates naturally varies depending upon the amount ratio of the cyclohexanedimethanol and bisphenol used. However, it has been found that when the amount ratio of the dihydroxy compounds is constant, the melt polymerization method gives a copolycarbonate having a higher amount ratio of the hetero-carbonates as compared with the solution polymerization method.
That is, when the amount ratio of the structural unit (I): structural unit (II) by molar ratio is m:n (provided that the total of m and n is 1), there is obtained a copolycarbonate resin having a hetero-carbonate content of at least (2.05xc3x97mxc3x97n), preferably at least (2.1xc3x97mxc3x97n) according to the present invention. In other words, the above content of the hetero-carbonate means the amount ratio of carbonate bonds formed of alternate arrangements of the structural unit (I) and the structural unit (II) in the main polymer chain, and it is the amount ration when the total of the carbonate bonds (m+n) is taken as 1.
The copolycarbonate resin having a hetero-carbonate content of at least (2.05xc3x97mxc3x97n) as described above is obtained as a copolycarbonate resin of which the structural unit (I) molar percentage based on the total of the structural unit (I) and the structural unit (II) is in the range of 15 to 85 mol %, by the melt-polymerization method. The copolycarbonate resin having a hetero-carbonate content of at least (2.05xc3x97mxc3x97n), particularly, at least (2.1xc3x97mxc3x97n) gives a lens having a refractive index, an Abbe""s number and a photoelasticity constant nearly equal to those of a lens given by a copolycarbonate resin having a smaller hetero-carbonate content than the above content. In the former copolycarbonate resin, however, the flowability (Q value) is improved with an increase in the hetero-carbonate content.
The copolycarbonate resin of the present invention comprises the structural unit (I) and the structural units (II), and it has been found that a plastic lens more improved in optical properties and heat resistance can be obtained by using a combination of specific two types included in the structural unit (II). Structural units of the above two specific types are represented by the following (II-a) and (II-b). (II-a) is a structural unit derived from bisphenol A that is used as the bisphenol. 
While the structural unit (II-b) is selected from the group consisting of the following (II-b-1) and (II-b-2), the unit of (II-b-1) is preferred. 
In the above structural units (II-b-1) and (II-b-2), each of R1 and R2 is independently an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a cycloalkyl group having 6 to 20 carbon atoms, a cycloalkoxy group having 6 to 20 carbon atoms, an aryl group having 6 to 10 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, an aralkyloxy group having 7 to 20 carbon atoms or a halogen atom, each of q and r is an integer of 0 to 4, Wxe2x80x2 is an alicyclic hydrocarbon group having 5 to 12 carbon atoms or a group represented by 
wherein R3 and R4 are the same as, or different from, each other and each is a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms, x is an integer of 1 to 5, each of R5 and R6 is independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, p is an integer of 4 to 7, each of R7 and R8 is independently a hydrogen atom, a halogen atom or an alkyl group having 1 to 3 carbon atoms, each of R11and R12 is independently an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a cycloalkyl group having 6 to 20 carbon atoms, a cycloalkoxy group having 6 to 20 carbon atoms, an aryl group having 6 to 10 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, an aralkyloxy group having 7 to 20 carbon atoms or a halogen atom, and each of y and z is an integer of 1 to 4.
Of the above structural unit (II-b), (II-b-1) is preferred, and further, the following units are particularly preferred as the (II-b-1). 
These units (i), (ii) (iii) and (vi) coming under (II-b) are structural units derived from (i) 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, (ii) 4,4xe2x80x2-dihydroxydiphenylsulfone, (iii) 9,9-bis(4-hydroxy-3-methylphenyl)fluorene and (vi) 1,1-bis(4-hydroxyphenyl)cyclohexane that are used as dihydroxy compounds.
The copolycarbonate resin having two types of the above structural unit (II) is composed of the structural units (I), (II-a) and (II-b). In this case, the molar percentage of the structural unit (I) based on the total of the structural unit (I) and the structural unit (II) (total of II-a and II-b) is 15 to 85%, preferably 20 to 80%, and the structural unit (II-a):structural unit (II-b) ratio by molar ratio is in the range of from 1:99 to 99:1, preferably 30:70 to 99:1, particularly preferably 40:60 to 95:5, most preferably in the range of from 50:50 to 90:10.
When two types of the structural unit (II) are used in combination as described above, there can be obtained a copolycarbonate resin and a plastic lens having a high glass transition temperature and an improved photoelasticity constant as compared with a case when (II-a) alone is used as a structural unit (II).
The copolycarbonate resin of the present invention can further contain a phosphorus-containing heat stabilizer for preventing a decrease in molecular weight and downgrading of a hue during molding. The heat stabilizer includes phosphorous acid, phosphoric acid, phosphinic acid, phosphonic acid and esters of these.
Specific examples of the heat stabilizer include triphenyl phosphite, tris(nonylphenyl) phosphate, tridecyl phosphate, trioctyl phosphite, trioctadecyl phosphate, didecylmonophenyl phosphate, dioctylmonophenyl phosphite, diisopropylmonophenyl phosphite, monobutyldiphenyl phosphite, monodecyldiphenyl phosphite, monooctyldiphenyl phosphite, tris(2,4-di-tert-butylphenyl)phosphite, bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite, 2,2-methylenebis(4,6-di-tert-butylphenyl)octyl phosphite, bis(nonylphenyl)pentaerythritol diphosphite, bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, distearylpentaerythritol diphosphite,
tributyl phosphate, triethyl phosphate, trimethyl phosphate, triphenyl phosphate, diphenylmonooxoxenyl phosphate, dibutyl phosphate, dioctyl phosphate, diisopropyl phosphate,
tetrakis(2,4-di-iso-propylphenyl)-4,4xe2x80x2-biphenylene diphosphonite, tetrakis(2,4-di-n-butylphenyl)-4,4xe2x80x2-biphenylene diphosphonite, tetrakis(2,4-di-tert-butylphenyl)-4,4xe2x80x2-biphenylene diphosphonite, tetrakis(2,4-di-tert-butylphenyl)-4,3xe2x80x2-biphenylene diphosphonite, tetrakis(2,4-di-tert-butylphenyl)-3,3xe2x80x2-biphenylene diphosphonite, tetrakis(2,6-di-isopropylphenyl)-4,4xe2x80x2-biphenylene diphosphonite, tetrakis(2,6-di-n-butylphenyl)-4,4xe2x80x2-biphenylene diphosphonite, tetrakis(2,6-di-tert-butylphenyl)-4,4xe2x80x2-biphenylene diphosphonite, tetrakis(2,6-di-tert-butylphenyl)-4,3xe2x80x2-biphenylene diphosphonite, tetrakis(2,6-di-tert-butylphenyl)-3,3xe2x80x2-biphenylene diphosphonite, bis(2,4-di-tert-butylphenyl)-biphenyl diphosphonite,
dimethyl benzenephosphonate, diethyl benzenephosphonate and dipropyl benzenephosphonate. Of these, tris(2,4-di-tert-butylphenyl)phosphite, tetrakis(2,4-di-tert-butylphenyl)-4,4xe2x80x2-biphenylene diphosphonite and bis(2,4-di-tert-butylphenyl)-biphenyl phosphonite are preferred.
These heat stabilizers may be used alone or in combination of two or more. The amount of the heat stabilizer per 100 parts by weight of the copolycarbonate resin is preferably 0.001 to 0.15 part by weight.
The copolycarbonate resin of the present invention may contain a fatty acid ester compound for improving the releasability of the resin from a mold when it is molded.
The above fatty acid ester is preferably a partial ester or a full ester from a monohydric or polyhydric alcohol having 1 to 20 carbon atoms and a saturated fatty acid having 10 to 30 carbon atoms. The partial ester or the full ester from a monohydric or polyhydric alcohol and a saturated fatty acid is preferably selected from stearic acid monoglyceride, stearic acid diglyceride, stearic acid triglyceride, stearic acid monosorbitate, behenic acid monoglyceride, pentaerythritol monostearate, pentaerythritol tetrastearate, pentaerythritol tetrapelargonate, propylene glycol monostearate, stearyl stearate, palmityl palmitate, butyl stearate, methyl laurate, isopropyl palmitate, biphenyl biphenate, sorbitan monostearate and 2-ethylhexyl stearate. Of these, stearic acid monoglyceride, stearic acid triglyceride and pentaerythritol tetrastearate are preferred. The amount of the fatty acid ester per 100 parts by weight of the copolycarbonate resin is preferably 0.001 to 0.5 part by weight.
The copolycarbonate resin of the present invention may further contain an ultraviolet absorbent for improving the resin in weatherability and intercepting undesired ultraviolet ray. Examples of the ultraviolet absorbent include benzophenone ultraviolet absorbents typified by 2,2xe2x80x2-dihydroxy-4-methoxybenzophenone, triazine ultraviolet absorbents typified by 2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5-hexyloxyphenol, and benzotriazole ultraviolet absorbents typified by 2-(2H-benzotriazol-2-yl)-4-methylphenol, 2-(2H-benzotriazol-2-yl)-4-tert-octylphenol, 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methy-1-phenylethyl)phenol, 2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol, 2-(5-chloro-2H-benzotriazol-2-yl)-4-methyl-6-tert-butylphenol, 2-(5-chloro-2H-benzotriazol-2-yl)-2,4-tert-butylphenol and 2,2xe2x80x2-methylenebis[6-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol]. These may be used alone or in combination of two or more. The amount of the ultraviolet absorbent per 100 parts by weight of the copolycarbonate resin is generally 0.01 to 1 part by weight, preferably 0.05 to 0.8 part by weight.
The copolycarbonate resin of the present invention may contain a bluing agent for offsetting a yellowish color caused by the polycarbonate resin or the ultraviolet absorbent when molded into a lens. Any bluing agent can be used without any limitation so long as it can be used in a polycarbonate resin. Generally, an anthraquinone dye is easily available and preferred.
Specifically, typical examples of the bluing agent include Common name Solvent Violet 13 (CA. No. (Color index No.) 60725; trade names xe2x80x9cMacrolex Violet Bxe2x80x9d supplied by Bayer AGxe2x80x3, xe2x80x9cDiaresin Blue Gxe2x80x9d supplied by Mitsubishi Chemical Co., Ltd., and xe2x80x9cSumiplast Violet Bxe2x80x9d supplied by Sumitomo Chemical Co., Ltd.), Common name Solvent Violet 31 (CA. No. 68210; trade name; xe2x80x9cDiaresin Violet Dxe2x80x9d supplied by Mitsubishi Chemical Co., Ltd.), Common name Solvent Violet 33 (CA. No. 60725; trade name; Diaresin Blue J supplied by Mitsubishi Chemical Co., Ltd.), Common name Solvent Blue 94 (CA. No. 61500; trade name; xe2x80x9cDiaresin Blue Nxe2x80x9d supplied by Mitsubishi Chemical Co., Ltd.), Common name Solvent Violet 36 (CA. No. 68210; trade name; xe2x80x9cMacrolex Violet 3Rxe2x80x9d supplied by Bayer AG), Common name Solvent Blue 97 (trade name xe2x80x9cMacrolex Violet RRxe2x80x9d supplied by Bayer AG), and Common name Solvent Blue 45 (CA. No. 61110; trade name xe2x80x9cTetrasole Blue RLSxe2x80x9d supplied by Sandoz AG). Generally, the bluing agent is incorporated into the copolycarbonate resin in an amount of from 0.3xc3x9710xe2x88x924 to 2xc3x9710xe2x88x924 per 100 parts by weight of the copolycarbonate resin.
The copolycarbonate resin of the present invention may contain a generally known antioxidant for preventing oxidation. Examples thereof include phenol antioxidants, and specific examples thereof include triethylene glycol-bis(3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate), 1,6-hexanediol-bis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, pentaerythritol-tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, N,N-hexamethylenebis(3,5-di-tert-butyl-4-hydroxyhydrocinnamide), 3,5-di-tert-butyl-4-hydroxybenzylphosphonate diethyl ester, tris(3,5-di-tert-butyl-4-hydroxybenzyl)isocyanurate and 3,9-bis{1,1-dimethyl-2-[xcex2-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl}-2,4,8,10-tetraoxaspiro(5,5)undecane. The amount of the antioxidant per 100 parts by weight of the copolycarbonate resin is preferably 0.0001 to 0.05 part by weight.
When the above copolycarbonate resin is used to produce a plastic lens, a known method can be employed. Specifically, the plastic lens of the present invention can be formed by any one of various molding methods, such as injection molding, compression molding, extrusion molding or injection compression molding. Injection compression molding is the most preferred since a lens free of an optical strain can be formed. In the injection compression molding, preferably, the cylinder temperature is 180 to 300xc2x0 C., and the mold temperature is 40 to 120xc2x0 C.
The plastic lens of the present invention may be surface-coated with a protective layer such as a hard coating layer, an anti-reflection coating layer or an anti-clouding coating layer. These protective layers will be explained later.
The plastic lens of the present invention can be applied to various lenses such as a spectacle lens, a camera lens, a binocular lens, a microscope lens, a projector lens, a Fresnel lens, a lenticular lens, fxcex8 lens, a headlamp lens, a pickup lens and the like. The plastic lens of the present invention is particularly the most suitably applied to a spectacle lens since it has an excellent balance between a refractive index and an Abbe""s number.
For a hard coating (cured) layer formed on the lens substrate surface in the present invention, both a thermosetting hard coating layer and an actinic ray curable hard coating layer can be preferably used.
The thermosetting hard coating material includes a silicone resin such as organopolysiloxane and a melamine resin.
The above silicone resin can be selected from resins described in JP-A-48-056230, JP-A-49-014535, JP-A-08-054501 and JP-A-08-198985. For example, the above hard coating layer made of a silicon resin is a hard coating layer formed by drying and/or heat-curing a coating composition comprising an organosilicon compound of the general formula
(R1)a(R2)bSi(OR3)4-(a+b)xe2x80x83xe2x80x83(*)
and/or a hydrolyzate thereof,
wherein each of R1 and R2 is independently an organic group selected from the class consisting of an alkyl group, an allyl group, an acyl group, a halogen group, a glycidoxy group, an epoxy group, an amino group, a phenyl group, a mercapto group, a methacryloxy group and a cyano group, R3 is an alkyl group having 1 to 10 carbon atoms, an alkoxy allyl group, an allyl group or an acyl group, and a and b are integers of 0 or 1.
Specific examples of the orgnosilicon compound include tetraalkoxysilanes such as methyl silicate, ethyl silicate, n-propyl silicate, iso-propyl silicate, n-butyl silicate, sec-butyl silicate and tert-butyl silicate or hydrolyzates of these, trialkoxysilanes such as methyltrimethoxysilane, methyltriethoxysilane, ethyltriethoxysilane, vinyltrimethoxysilane, phenyltrimethoxysilane, xcex3-chloropropyltrimethoxysilane, xcex3-mercaptopropyltrimethoxysilane, xcex3-methacryloxypropyltrimethoxysilane, xcex3-aminopropyltrimethoxysilane, xcex3-glycidoxypropyltrimethoxysilane, (3,4-epoxycyclohexyl)methyltrimethoxysilane, (3,4-epoxycyclohexyl)ethyltrimethoxysilane and xcex3-(3,4-epoxycyclohexyl)propyltrimethoxysilane or hydrolyzates of these, and dimethoxysilanes such as dimethyldimethoxysilane, dimethyldiethoxysilane, phenylmethyldimethoxysilane and xcex3-glycidoxypropylmethyldimethoxysilane or hydrolyzates of these.
These organosilicon compounds may be used alone or in combination of two or more.
The above organosilicon compounds are preferably used after hydrolyzed, for decreasing a curing temperature and promoting the curing. The hydrolysis is preferably carried out in the presence of an inorganic acid such as hydrochloric acid or sulfuric acid or an organic acid such as acetic acid. The degree of the hydrolysis can be easily controlled by adjusting the amount of the acid used. For carrying out uniform hydrolysis, an organic solvent may be used. The organic solvent is selected from an alcohol, a ketone, an ether, a cellosolve or an aromatic hydrocarbon. These solvents may be used alone or in combination of two or more.
The hard coating layer made of the melamine resin is a hard coating layer formed by drying and/or heat-curing a coating composition containing a melamine resin such as methylated methylolmelamine, propylated methylolmelamine, butylated methylolmelamine or isobutylated methylolmelamine, a crosslinking agent, a curing agent, and the like.
The above melamine resins may be used alone or in combination of two or more. Further, the hard coating layer may contain a modifier such as an acrylic resin, a polyether resin, a polyester resin or a silicone resin so long as the physical properties thereof are not impaired.
Examples of the curing agent include inorganic acids such as hydrochloric acid, sulfuric acid and nitric acid and organic acids such as oxalic acid, oxalic acid, maleic acid and p-toluenesulfonic acid.
Examples of the crosslinking agent include short-chain glycols such as ethylene glycol, diethylene glycol, butanediol and hexanediol and long-chain glycols such as polyethylene glycols. These may be incorporated alone or in combination of two or more.
In the melamine coating composition, the amount of each of the curing agent and the crosslinking agent is determined depending upon a purpose. The criterion of determination of the amount of the crosslinking agent is that the functional group of the melamine resin and the functional group of the crosslinking agent are equimolar. The amount of the crosslinking agent per 100 parts by weight of the melamine resin is preferably 10 to 200 parts by weight, more preferably 20 to 150 parts by weight. The amount of the curing agent per 100 parts by weight of the melamine resin is preferably 1 to 10 parts by weight, more preferably 2 to 7 parts by weight.
The solvent includes an alcohol, a ketone, an ether, a cellosolve and an aromatic hydrocarbon. These solvents may be used alone or in combination of two or more.
The actinic ray curing hard coating material can be selected from materials described in JP-A-54-097633, JP-A-03-145602 and JP-A-2000-229384. For example, the above material includes a polyfunctional compound having at least two actinic ray curable functional groups, such as compounds having unsaturated group, as the actinic ray curable functional groups, (meth)acryloyl groups, vinyl groups or allyl groups, preferably compounds having (meth)acryloyl groups. For example, the material is a poly(meth)acrylate formed from a compound having at least two hydroxyl groups such as polyhydric alcohol and (meth)acrylaic acid.
The above poly(meth)acrylate compound specifically includes the following compounds. For example, it includes 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, cyclohexanedimethanol di(meth)acrylate, polyethylene glycol di(meth)acrylate, glycerol tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tris(2-(meth)acryloyloxyethyl)isocyanurate, bis(2-(meth)acryloyloxyethyl)-2-hdyroxylethylisocyanurate, tris(2-(meth)acryloyloxypropyl)isocyanurate, bisphenol A dimethacrylate, tri(meth)acrylate of ethylene-oxide-added trimethylolpropane, tetra(meth)acrylate of ethylene-oxide-added pentaerythritol, hexa(meth)acrylate of ethylene-oxide-added dipentaerythritol and hexa(meth)acrylate of caprolactone-added dipentaerythritol.
Preferred are trimethylolpropane poly(meth)acrylate, pentaerythritol poly(meth)acrylate and isocyanurate poly(meth)acrylate.
In addition to the actinic ray curable functional groups, the above polyfunctional compound may have various functional groups and bonds such as a hydroxyl group, a carboxyl group, a halogen group, a urethane bond, an ether bond, an ester bond, a thioether bond, an amide bond and a diorganosiloxane bond. Particularly preferred is a (meth)acryloyl-group-containing compound having a urethane bond (to be sometimes referred to as xe2x80x9cacrylurethanexe2x80x9d hereinafter).
The acrylurethane included in the above polyfunctional compound includes a reaction product from a compound (1) having at least two isocyanate groups per molecule, a compound (2) having at least two hydroxyl groups per molecule, and a compound (3) having a hydroxyl group and a (meth)acryloyl group.
The compound (1) having at least two isocyanate groups per molecule includes 2,6-tolylene diisocyanate, 2,4-tolylene diisocyanate, diphenylmethane-4,4-diisocyanate, dicyclohexylmethane-4,4-diisocyanate, hexamethylene diisocyante, tetramethylene diisocyanate, phenylene diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, 1,5-naphthalene diisocyanate, cyclohexane diisocyanate and isophorone diisocyanate.
The compound (2) having at least two hydroxyl groups per molecule includes polyhydric alcohols such as ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, cyclohexanedimethanol, diethylene glycol, trimethylolpropane, pentaerythritol, ditrimethylolpropane, dipentaerythritol and tris(2-hydroxyethyl)isocyanurate, polyalkylene glycols such as polyethylene glycol and polypropylene glycol, and polyester polyols obtained by condensation of the above polyhydric alcohols or polyalkylene glycols with polybasic acids (such as phthalic acid, terephthalic acid and maleic acid) or anhydrides thereof.
Specific examples of the compound (3) having a hydroxyl group and a (meth)acryloyl group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxy-3-chloropropyl (meth)acrylate, 4-hydroxycyclohexyl (meth)acrylate, 2-hydroxy-3-phenyloxypropyl (meth)acrylate and pentaerythritol acrylate.
The above acrylurethane that is a specifically preferred polyfunctional compound includes an acrylurethane that is a product from pentaerythritol or polypentaerythritol that is a polymer thereof, polyisocyanate and hydroxyalkyl (meth)acrylate, and an acrylurethane that is a reaction product from hydroxyl group-containing poly(meth)acrylate of pentaerythritol or polypentaerythritol and polyisocyanate.
When the curing is carried out with ultraviolet ray (UV) out of actinic rays for curing, a photopolymerization initiator is used. The above photopolymerization initiator includes aryl ketone photopolymerization initiators (such as acetophenones, benzophenones, benzoins and benzoin ethers), sulfur-containing photopolymerization initiators (such as sulfides and thioxantones), an acylphosphine oxide photopolymerization initiator, a diacylphosphine oxide photopolymerization initiator and other photopolymerization initiators.
The amount of the above photopolymerization initiator per 100 parts by weight of the UV-curable polyfunctional compound is preferably 0.01 to 20 parts by weight, particularly preferably 0.1 to 10 parts by weight.
For adjusting the coating composition to a proper viscosity, an organic solvent may be incorporated. The organic solvent includes an alcohol, a ketone, an ether, a cellosolve and an aromatic hydrocarbon. These solvents are used alone or in combination of two or more.
In addition to the above components, the coating composition may contain other components so long as the properties of a cured layer are not impaired. For example, the coating composition may contain a curing agent for promoting the reaction, an inorganic substance having the form of fine particles for adjusting the refractive index of the coating to the counterpart of various substrates, and various surfactants for improving wettability during application or the smoothness of a cured layer.
For improving a surface hardness, it is particularly suitable to use a colloidal silica that is a colloidal dispersion of high-molecular-weight anhydrous silicic acid in water and/or an organic solvent such as an alcohol. As a colloidal silica, it is preferred to use a dispersion of silica fine particles having a particle diameter of 1 to 100 xcexcm. Further, the colloidal silica is preferably used in the amount range of 5 to 70% by weight for improving adhesion to an anti-reflection layer.
The coating may be colored by dispersing a colorant (a dye and a pigment) or a filler or by dissolving an organic polymer. Further, an ultraviolet absorbent and an anti-oxidant may be added.
The means for applying the coating composition to a substrate (plastic lens) is not restricted, and there may be employed known methods such as a dipping method, a spraying method, a spin coating method, a bar coating method, a flow coating method and a roll coating method. In view of surface accuracy, a dipping method and a spin coating method are preferred.
The coating composition applied onto the substrate is cured in the following manner, to form a hard coating layer. When the coating composition is a thermosetting hard coating material, it is cured by drying and/or heating after applied onto the substrate.
The temperature for drying and/or heating is preferably in the range of from 50xc2x0 C. to 200xc2x0 C., particularly preferably in the range of from 70xc2x0 C. to 150xc2x0 C.
The drying and/or heating is carried out until the cured layer has a sufficient hardness, and with an increase in the heating temperature, the time period required therefor decreases. The drying and/or heating may be carried out for 0.3 to 5 hours.
The actinic ray curable hard coating material is cured by irradiation with actinic ray such as UV ray, electron beam or laser, after applied to the substrate. While the actinic ray is not specially limited, UV ray is preferred. The source of the UV ray can be selected from a xenon lamp, a pulse xenon lamp, a low-pressure mercury lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a metal halide lamp, a carbon arc lamp or a tungsten lamp.
For improving adhesion between the substrate and the hard coating layer, preferably, the substrate is pre-treated before the application of the coating composition. Examples of the pre-treatment include chemical treatment with an acid, an alkali or an organic solvent, physical treatment with plasma or ultraviolet ray, washing with various detergents, and primer treatment with various resins.
The hard coating layer cured by the above method preferably has a thickness of 1 to 50 xcexcm. When the above thickness exceeds 50 xcexcm, the curing is insufficient, and the adhesion to the substrate is liable to be impaired. When it is less than 1 xcexcm, an outermost layer formed on this layer may fail to exhibit sufficient abrasion resistance and scratch resistance.
A single-layered or multi-layered anti-reflection layer may be formed on the above cured layer as required. The component for forming the anti-reflection layer is selected from known components such as inorganic oxides, fluorides or nitrides. Specific examples of the component include silicon dioxide, silicon monoxide, zirconium oxide, tantalum oxide, yttrium oxide, aluminum oxide, titanium oxide, magnesium fluoride and silicon nitride. The method for forming the above layer includes a vacuum deposition method, a sputtering method, an ion plating method and an ion beam assisting method. When the anti-reflection layer is formed, the lens is improved in anti-reflection performances. Further, an anti-clouding layer may be formed on the above cured layer or the above anti-reflection layer.
While the copolycarbonate resin of the present invention is useful for a plastic lens as described above, it has been found that the copolycarbonate resin of the present invention can give useful and high-performance molded articles on the basis of its excellent transparency, optical properties and flowability when molded into other optical molded article sheets and films.
According to the present invention, there is provided an optical molded article made of a copolycarbonate resin comprising the foregoing structural unit (I) and the foregoing structural unit (II), having a structural unit (I) molar percentage of 15 to 85% based on the total of the structural units (I) and (II) and having a specific viscosity of 0.25 to 0.6.
The above optical molded article can be any one of an optical disk substrate, a light diffusing plate, a light guiding plate, an optical card, an optical prism and an optical fiber. In a use other than the optical molded articles, the copolycarbonate resin of the present invention can be applied, for example, to a binder for an electrophotographic photoreceptor.
The copolycarbonate resin for the optical molded article preferably has a phenolic hydroxyl group (OH group) terminal content in the range of from 1 to 80 mol %, preferably from 2 to 70 mol %, based on the total content of terminals. Further, the copolycarbonate resin preferably has a structural unit (I) molar percentage of 20 to 80%, particularly preferably 30 to 70%, based on the total of the structural units (I) and (II), and further preferably, it has a specific viscosity in the range of from 0.25 to 0.56. The copolycarbonate resin further advantageously has a molecular weight distribution (Mw/Mn) in the range of from 1.1 to 3, preferably in the range of from 1.3 to 2.8.
An optical disk substrate is a typical example of the optical molded article. The optical disk substrate covers a compact disk for audio (recording density of approximately 650 MB per disk having a diameter of 12 cm) up to a high-density disk substrate. For example, DVD-ROM having a capacity of 4.7 GB for reproduction only is recently realized, and a capacity of 4.7 GB is being materialized for DVD-R, DVD-RW and DVD-RAM that permit recording and reproduction. As an MO disk having a size of 5.25xe2x80x3, optical information recording media having a capacity of 5.2 GB on two surfaces are put on the market, and as an MO disk having a size of 3.5xe2x80x3, optical information recording media having a capacity of 1.3 GB on one surface are put on the market. And, for coping with digital high-resolution broadcasting, there is desired a high-density optical recording medium having a capacity of approximately 6.5 GB or more, particularly, 10 GB or more on one surface as a disk having a diameter of 12 cm. The optical disk substrate of the present invention has properties adequate for application and adaptation thereto.
The optical disk substrate gives an optical disk when a metal thin layer is formed on at least one surface thereof. The metal includes aluminum, Tb, Fe, Co, Gd, SiN, ZnSxe2x80x94SiO2, GeSbTe, ZnS and an aluminum alloy, and aluminum is suitable. The thin layer can be formed by means such as sputtering or vapor deposition. These means for forming the metal thin layer can be carried out by methods that are known per se.
The optical disk substrate can be obtained by molding the above copolycarbonate resin according to any method such as an injection molding method, a compression molding method or an extrusion method. For the optical disk of the present invention, an injection molding method is excellent in productivity and is therefore suitable.
The optical disk substrate is generally obtained by injection-molding the above polycarbonate resin at a resin temperature of 250 to 380xc2x0 C. at a mold temperature of 60 to 130xc2x0 C., or the optical disk substrate may be a disk formed by bonding thus-obtained substrates to each other.
According to the present invention, further, there is provided a film or a sheet formed of a copolycarbonate resin comprising the foregoing structural units (I) and (II), having a structural unit (I) molar percentage of 15 to 85% based on the total of the structural units (I) and (II) and having a specific viscosity of 0.3 to 0.7.
The copolycarbonate resin forming the film or the sheet preferably has a phenolic hydroxyl group (OH group) terminal content in the range of from 1 to 80 mol %, preferably from 2 to 70 mol %, based on the total content of terminals. Further, the copolycarbonate resin preferably has a structural unit (I) molar percentage of 20 to 80%, particularly preferably 30 to 70%, based on the total of the structural units (I) and (II), and further advantageously, it has a specific viscosity in the range of from 0.3 to 0.6 for the sheet or in the range of from 0.35 to 0.7 for the film. The copolycarbonate resin further advantageously has a molecular weight distribution (Mw/Mn) in the range of from 1.1 to 3, preferably in the range of from 1.3 to 2.8.
The sheet desirably has a thickness in the range of from 0.6 to 10 mm, particularly desirably in the range of from 0.8 to 8 mm. The film has a smaller thickness than the sheet, and the film generally has a thickness in the range of from 1 to 600 xcexcm, preferably in the range of from 10 to 500 xcexcm.
The film and the sheet can be produced by a method that is known per se.
For example, when the sheet is produced, a powder or pellets of the polycarbonate resin and predetermined amounts of additives (heat stabilizer, anti-oxidant, ultraviolet absorbent, mold release agent, colorant, etc.) are homogeneously mixed with any mixing means such as a tumbler, a V-type blender or a high-speed mixer, and the obtained mixture is molded, directly or after once pelletized with a vented single-screw or twin-screw extruder the pellets are molded, into a sheet-typed polycarbonate resin molded article by any method such as injection molding, extrusion molding, compression molding or rotary molding. Of these, a method of obtaining a sheet-shaped molded article by injection molding and a method of obtaining a resin plate (sheet) by extrusion molding are suitably employed, and an extrusion molding method is preferred. The method of obtaining a resin plate by extrusion molding includes a method in which a molten polycarbonate resin extruded with an extruder with a T die is taken up with cooling it with a cooling roll. In this case, the cooling roll is preferably set at a temperature in the range of from 50 to 200xc2x0 C., particularly preferably in the range of from 60 to 120xc2x0 C. The sheet can be suitably applied to a window glass and roof of an automobile, optical materials such as a phase difference plate, a polarizer and a light diffusing plate, building materials such as a wall material, a floor material, an arcade roof material, a veranda baseboard, a wind-shielding plate and a snow-shielding plate, a display case, a show window, various trays, various panels (instrument board protection cover), a shield for a helmet, and the like.
On the other hand, the method of forming the film is preferably a method which can provide a film excellent in thickness uniformity, which does not cause a gel, a fisheye, a scratch, etc., and which gives a film containing little foreign matter, and the method includes a solvent casting method, a melt-extrusion method and a calender method. When the film is used in an optical field, the film is required to have high uniformity, so that it is preferred to employ a method of solution casting. Generally, the casting method is preferably selected from a casting method in which a solution is extruded through a die or a doctor knife method. Examples of the solvent preferably include organic solvents such as methylene chloride, chloroform, dioxolane, toluene, dimethylformamide and N-methylpyrrolidone. These solvents may be used alone, or a mixture of at least two solvents may be used. A solution having a concentration of 5 to 50 wt % is preferably used.
The film produced by the above method can be suitably applied to a screen film of a television set, a phase difference film, a polarizing film, a display screen such as a plastic cell film and an insulating film.
According to the present invention, further, there is provided a copolycarbonate resin (A) (i) comprising the foregoing structural units (I) and (II), (ii) having a structural unit (I) molar percentage of 15 to 85% on the basis of the total of the structural units (I) and (II), (iii) having a specific viscosity of 0.3 to 0.7 and (iv) having a phenolic hydroxyl group (OH group) terminal content in the range of from 1 to 80 mol % based on the total terminal content.
In the above copolycarbonate resin (A), preferably, the structural unit (I) is represented by the following structural unit (Ixe2x80x2), and in the steric configuration of two methylene groups bonding to 1,4-cyclohexylene group in the formula (Ixe2x80x2), the trans/cis ratio is preferably in the range of from 100/0 to 50/50.
In the above copolycarbonate resin (A), more excellently, (ii) the molar percentage of the structural unit (I) based on the total of the structural units (I) and (II) is 20 to 80 mol %, and (iv) the content of the phenolic hydroxyl terminal group based on the total content of the total terminal group is in the range of from 2 to 70 mol %. Further, advantageously, the molecular weight distribution (Mw/Mn) is in the range of from 1.1 to 3.0, preferably in the range of from 1.3 to 2.8.
In the above copolycarbonate resin (A), more excellently, the structural unit (II) is the following structural unit (II-a). 
In the above copolycarbonate resin (A), preferably, the structural unit (I) is represented by the above structural unit (Ixe2x80x2), and the structural unit (II) is a combination of the following structural units (II-a) and (II-b). 
While the structural unit (II-b) is selected from the group consisting of the following (II-b-1) and (II-b-2), the unit (II-b-1) is more preferred. 
In the above units (II-b-1) and (II-b-2), each of R1 and R2 is independently an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a cycloalkyl group having 6 to 20 carbon atoms, a cycloalkoxy group having 6 to 20 carbon atoms, an aryl group having 6 to 10 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, an aralkyloxy group having 7 to 20 carbon atoms or a halogen atom, each of q and r is an integer of 0 to 4, Wxe2x80x2 is an alicyclic hydrocarbon group having 5 to 12 carbon atoms or a group represented by the following, 
wherein R3 and R4 are the same as, or different from, each other, and each is a hydrogen atom or a hydrocarbon group having 1 to 10 carbon atoms, x is an integer of 1 to 5, each of R5 and R6 is independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, p is an integer of 4 to 7, each of R7 and R8 is independently a hydrogen atom, a halogen atom or an alkyl group having 1 to 3 carbon atoms, each of R11 and R12 is independently an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a cycloalkyl group having 6 to 20 carbon atoms, a cycloalkoxy group having 6 to 20 carbon atoms, an aryl group having 6 to 10 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, an aralkyloxy group having 7 to 20 carbon atoms or a halogen atom, and each of y and z is an integer of 1 to 4.
Of the above structural unit (II-b), (II-b-1) is preferred, and further, the following units are particularly preferred as the (II-b-1). 
These units (i), (ii) (iii) and (vi) coming under (II-b) are structural units derived from (i) 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, (ii) 4,4xe2x80x2-dihydroxydiphenylsulfone, (iii) 9,9-bis(4-hydroxy-3-methylphenyl)fluorene and (vi) 1,1-bis(4-hydroxyphenyl)cyclohexane that are used as dihydroxy compounds.
The copolycarbonate resin having two types of the above structural unit (II) is composed of the structural units (Ixe2x80x2), (II-a) and (II-b). In this case, the molar percentage of the structural unit (Ixe2x80x2) based on the total of the structural unit (Ixe2x80x2) and the structural unit (II) (total of II-a and II-b) is 15 to 85%, preferably 20 to 80%, and the structural unit (II-a):structural unit (II-b) ratio, by molar ratio, is in the range of from 1:99 to 99:1, preferably 30:70 to 99:1, particularly preferably 40:60 to 95:5, most preferably in the range of from 50:50 to 90:10.
When two types of the structural unit (II) are used in combination as described above, there can be obtained a copolycarbonate resin and a molded article having a high glass transition temperature and an improved photoelasticity constant as compared with a case when (II-a) alone is used as a structural unit (II).
The above copolycarbonate resin (A) can be produced by polymerizing dihydroxy compounds which are 15 to 85 mol % of cyclohexanedimethanol of the following formula (I-R) and 85 to 15 mol % of bisphenol of the following formula (II-R) and a carbonate ester according to an ester-exchange method. 
In the formula (II-R), R1, R2, W, q and r are as defined concerning the foregoing structural unit (II).